This invention relates generally to a rotary internal gear machine of the type having a centered outer gear supported for rotation about a center axis and an inner gear supported for performing a wobbling movement around the center axis in engagement with the outer gear.
Machines of this type are known in principle from the prior art, for example from the German publication 1,703,406, German Pat. No. 1,528,998 and German patent 1,528,997. Such prior-art machines, however, are equipped with the same control systems as conventional rotary disk machines, that means the fluid displacement unit formed of the inner and outer gears is separated from a hydraulic distributor by means of stationary or movable control plates. From a German publication No. 2,240,632 a control plate is known which forms simultaneously a boundary wall for the fluid displacement unit whereby the control openings formed in the control plate are situated in a central range of the latter and another control plate cooperating with the first-mentioned plate is arranged in a central recess of the outer gear. The flow of the working fluid from the control part to respective pockets or chambers in the fluid displacement unit or vice versa takes place via an additional intermediate piece arranged in a central recess of the internal outer gear, the intermediate piece having a plurality of distributing channels cooperating with connecting channels in the rotary outer gear. This arrangement in which the control part is situated in the central range of the outer gear is suitable for relatively small streams of working fluid and thus for small rotary speeds since the control opening in the control part can be formed with small clearance only.